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I received the UMX-3 and wired it up for a test to the 12-24v DC-DC converter, a Shure SM11 mic and an output cable. Everything appears to work. The VU meter on the mixer seems to work fine. I have not yet noticed any noise from the DC-DC converter, but did not fully test yet.
I also did some in-car measurements of wind noise, windows down. The roll bar SCHD location is the WORST place in the car for wind noise. Anywhere forward in the car appears to be a good spot. Behind the rear view mirror is a nice quiet spot for wind, but my mirror rattles, so that's out. I'm thinking the storage area beneath the HVAC controls is a good spot to test with an actual mic (SM11) mixed with the exhaust/road mic.
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I'm not sure if you saw, but AiM just released a firmware update for the SCHD. I haven't played with it yet (I'm working sway bar rates all day), but it the release history says "Developed compatibility with pre-amplified microphones." Sounds like that might be just what you need.
I'm not sure if you saw, but AiM just released a firmware update for the SCHD. I haven't played with it yet (I'm working sway bar rates all day), but it the release history says "Developed compatibility with pre-amplified microphones." Sounds like that might be just what you need.
Well, I've been through the menus and didn't notice anything different. Would you be able to check with AIM to see how this is implemented? While your asking, generally stated, I'm looking to couple a mic or line level input to the SCHD through the external MIC cable.
Unfortunately, from the cable specs (and the cable specs for the external mic cable) it appears as though the SCHD input is designed to interface directly to an electret condensor mic element. This results in an input incompatible with a simple line or mic level output. Electret mics require a bias voltage which do not permit simply passing a signal from a mixer or preamp to the input. I can build a little circuit to make this work, but this will take some time. Here's an example ('line to electret mic):
I have success. Built a small circuit to convert line level to a condenser mic input of the SCHD.
Calibrated levels. Used 3/4 external level on SCHD.
Peak on the little preamp mixer matches peak in the recorded .MOV file per below. Thus, I am utilizing the full dynamic range of the SCHD audio.
I have yet to try with the motor on as this may introduce some electrical noise.
More tomorrow.
Big issues with electrical noise. This will take awhile.
Now I know when all these systems use Condenser mics in the car.
Dynamic mics pick up way too much car electrical noise.
Mostly (90%) solved by adding an audio isolation transformer in line with the voltage divider and DC block capacitor. I'm trying a few other things on order. Trying to stay 'off the shelf' if possible to enable easy recreation by others.
In the meantime, I added a cheap condenser lavalier to the external mic input of the SCHD and placed the mic near the HVAC dash control. It's out of the wind there and sounds great. Likely all I'll really need, but that never stopped me.
With the audio, my generalized end goal for this forum is to provide a simple and off the shelf way to add a line level input to a SCHD for whatever purpose people want. This will allow all sort of interesting things including various setups with multiple mics which is my personal goal.
After much failure using the small mixer preamp discussed above with minor engine noise, I decided to start with an easier solution, using a multichannel audio recorder as a mixer preamp.
So, I started with a Zoom H5 recorder mounted using a combo of ProClip and RAM parts near the HVAC. I choose this spot due to good cabin ambient pickup but low wind noise.
This was wired to USB power from the car; and uses its built in mic for the cabin and a Shure SM11 attached at the license plate for relatively wind free exhaust and road audio. You can see the XLR connector from this at the bottom left of the H5.
Here is the plate mic.
The output of the H5 (the line out set to 0db level) goes to a 1/8" to XLR adapter (make sure to lift ground) and to a Shure A96F Camcorder interface.
This interface adapts the output of the H5 to a condensor mic input of the SmartyCam (using the CAN BUS EXTERNAL MIC CABLE).
I mounted the A96F on the cage near the SCHD.
Last but not least here's a little test on the driveway.
I've improved the sound quite a bit.
I added some substantial compression to the rear-plate mic as well as the in-cabin mic and made some other adjustments. All internal to the Zoom mixer/recorder. The only thing now missing is an audio feed from an intercom. However, with the added compression, the in-cabin mic does pic up instructor audio as can be heard here. Great few days at Thompson with PCA NER!
04-13-2017, 10:00 PM
